1. Field of the Invention
The invention relates to a burner for an industrial furnace in which there is arranged in the furnace space a combustion chamber in which a mixture of fuel gas and burner air is combusted, and from which a flame is directed into the furnace space.
2. Description of the Related Art
A burner of the aforesaid type is known from EP-PS 0 164 576.
In the known burner, the combustion chamber is configured as a short tube segment that tapers at the end towards the combustion space and has an opening for emergence of the flame, while the end of the combustion chamber opposite the combustion space consists of a radial plate that is set on the inner end face of the tube.
Present in the radial plate, on one periphery thereof, are openings that allow burner air to enter the combustion chamber. A tubular gas lance is guided through a centered opening in the plate into the interior of the combustion chamber. The gas lance extends into the outer space of the industrial furnace, where fuel gas is applied to it. The aforesaid burner air is supplied to the rear side of the radial plate via an interior space of a recuperator arrangement. The burner air supplied in this manner is, however, divided in the region of the aforesaid radial plate into two partial flows, one of which enters the combustion chamber through the radial plate, while the other flows axially past the combustion chamber and is mixed into the flame as secondary air at the front end of the combustion chamber. For this purpose a nozzle support is provided, which holds the combustion chamber around the front opening in an annular manner by elastically retaining it.
The gas lance is equipped with an electrode that extends axially through it, which extends into the combustion chamber and there ignites a gas/air mixture when the burner is started up.
The known burner thus has the following disadvantages:
Because the combustion chamber consists only of a short tube segment that is sealed off on the inside by the radial plate, the volume of the combustion chamber cannot be modified. A variety of burners are therefore required for different burner outputs and possibly also for different utilization conditions, the design of which must be adapted in each case to the desired combustion chamber volume.
The sealed construction of the combustion chamber in the known burners on the furnace end thereof furthermore has the disadvantage that disassembly of the combustion chamber is very complex, since for this purpose the entire burner must be removed, i.e. pulled out from the industrial furnace, since the combustion chamber is not accessible from outside.
Furthermore, the arrangement of the ignition electrode in the combustion chamber has the disadvantage that an unfavorable gas/air mixture is always present in the combustion chamber in conjunction with the delivery of burner air as the burner is started up. Specifically, if a portion of the burner air is carried past the combustion chamber as secondary air, and if, for example, only 70% of the burner air supplied reaches the combustion chamber, this can cause problems during a cold start of the burner. Although attempts have been made to solve this known problem by delivering less gas when the burner is being started, so that the gas/air mixture in the combustion chamber is optimized for ignition, this trick nevertheless requires additional effort in adjusting the burner, especially during starting, and complicates automatic operation.